A machine-readable graphical code (“graphical code”) is a graphical representation of information that consists of multiple graphical code elements having different light reflective or light emissive properties. Examples of different types of graphical codes include bar codes, data matrix codes, MaxiCodes, and so forth. Graphical codes have become widely used in many commercial environments, such as point-of-sale stations in retail stores and supermarkets, inventory and document tracking, and the like.
Devices for identifying or extracting information from graphical codes are generally referred to as graphical code readers. Image-based graphical code readers typically include one or more light sources for illuminating a graphical code. Light is reflected from the graphical code toward the graphical code reader. A lens within the graphical code reader focuses an image of the graphical code onto an image sensor. Pixels within the image sensor are read electronically to provide a two-dimensional array of image data corresponding to the graphical code. A decoder then processes the image data and extracts the information contained in the graphical code.
Graphical codes may be encoded according to a wide variety of different symbologies. A symbology is a protocol for arranging the graphical code elements that make up a particular kind of graphical code. In some symbologies, the same information is contained throughout the height of the code, making such codes vertically redundant. Some examples of such linear or one-dimensional graphical code symbologies are UPC, Code 128, Code 39, Interleaved 2 of 5, Codabar, MSI Plessey, Code 93, etc. Graphical codes that are encoded in accordance with two-dimensional graphical code symbologies are also commonly used. Some examples of two-dimensional graphical code symbologies are GoCode, Maxicode, PDF 417, Data Matrix, Datastrip, etc.
Two-dimensional graphical codes possess several advantages over one-dimensional graphical codes. For example, two-dimensional graphical codes are designed to store considerably more information than one-dimensional graphical codes. In addition, two-dimensional graphical codes are typically smaller than one-dimensional codes. Also, in some cases, two-dimensional graphical codes do not require a high level of print quality in order to be decoded.
Some graphical code readers are capable of decoding different graphical code symbologies. Such graphical code readers typically include multiple decoders, each of which is configured to decode a specific graphical code symbology. In such a graphical code reader, benefits may be realized by improvements in the way that the multiple decoders are managed during various stages of the decoding process.